As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
One or more cooling fans are typically employed within the chassis of information handling systems, such as servers, to cool components operating within the information handling system chassis. Such cooling fans may be uncontrolled, i.e., running at full power whenever the information handling system is a powered on state. However, cooling fans consume power, create noise, and create airflow, each of which becomes of greater concern in a data center where a plurality of information handling systems may be operating, e.g., as servers. Cooling fans may also be controlled based on ambient temperature within an information handling system chassis.
Thermal control techniques have been developed for information handling systems in an attempt to reduce power consumption, airflow and acoustic noise generated by cooling fans. Such techniques include proportional-integral-derivative (PID) control loop feedback. There has also been a push to increase the number and type of components mapped into thermal control for a given information handling system. In particular, there has been a desire to include hard disk drive (HDD) and redundant array of independent disks (RAID) hardware (RAID card) temperature information for thermal control due to the manner in which these components drive open loop fan requirements for shipped information handling systems, such as servers. By implementing thermal control using temperature information from such additional components, fan speeds can be reduced for normal operation while at the same time allowing improved coverage on high stress conditions.
Direct mapping of cooling fan speeds to HDD and RAID hardware temperatures has proven problematic for several reasons. First, updating temperatures from such hardware components at the rate that is typically used for PID thermal control (1 to 5 seconds) has pronounced adverse performance impacts on HDD throughput and latency. Moreover, relatively slow component response times (in the order of minutes) causes concerns when using PID control due to interaction with memory and central processing unit (CPU) PID input which is typically on the order of seconds.
Thermal control techniques have been implemented for RAID servers that control cooling fan speeds based on HDD and battery temperature response. The scoped temperature response time for such HDD and battery hardware components is once every 5 seconds. However due to performance impacts on the hardware RAID card of the server, the temperature response time is set at 1 minute for battery hardware and 5 minutes for HDD components. Thus temperature updates are slower than the response time of the components to a transient load change (See FIGS. 1 and 2) which makes mapping fan speed response to component temperature changes difficult. Moreover thermal response of different components may vary differently over time with changes in load, as illustrated in FIG. 2 for the battery and controller components of a RAID card, which makes thermal control of such components together difficult. The combination of component thermal mass and temperature polling rates causes disconnect in thermal control response to temperature inputs that needs to be addressed.
Hardware components with fast temperature response times (1-5 seconds) have been mapped directly into cooling fan thermal control using traditional closed loop control with either PID or guard band approaches. However, when temperature response times are slower (10-300 seconds) closed loop approaches can cause fan speeds to quickly go to full speed. Conventional closed loop response looks for a temperature change once every second and in absence of temperature update speeds up of the fans at a minimum of 1% PWM per second. When such conventional closed loop control does not receive HDD and battery temperature updates for periods of time greater than 60 seconds, closed loop thermal control quickly drives fans to full speed with corresponding acoustic and fan power impacts. This can be mitigated to some degree by changing the fan speed response time to be closer to the closed loop response time of the component. However, in this case the closed loop response time is not fast enough for PID to respond adequately with fan speed overshoot causing oscillation in fan speeds.
Open loop power capping techniques have been employed for an information handling system based on measured system inlet ambient temperature. Such techniques initiate power capping of system components based on temperature when measured inlet ambient temperature meets or exceeds a maximum inlet ambient temperature threshold, but do not initiate power capping based on temperature as long as measured inlet ambient temperature remains below the maximum inlet ambient temperature threshold. As a result, higher fan speeds and/or power capping may be implemented even when individual hardware components do not actually need additional cooling.